Public Release: 5-Jan-2005
Scientists observe largest explosion in space

ATHENS, Ohio - Scientists have observed the largest explosion in space, a finding that suggests that supermassive black holes - which produced the blast - are a bigger force to be reckoned with in the universe than previously thought.

The study, published in this week's issue of the journal Nature, details the discovery of enormous cavities - each about 650,000 light years across - surrounded by hot gas in a distant cluster of galaxies. The two cavities, created by an outburst from a supermassive black hole, could explain why some galaxies don't create new stars as they cool down in temperature - the typical recipe for star formation, said Brian McNamara, an Ohio University astronomer who is lead author on the research.

NASA's Chandra X-ray Observatory detected the explosion, which isn't visually spectacular but is massive and very powerful, "like a nuclear blast without the light," he said. While the astronomer previously has spotted and studied these cosmic bubbles of hot gas elsewhere in the universe, "what literally almost knocked me off my chair was the scale, the magnitude of this," said McNamara, an associate professor of physics and astronomy.

Chandra observed the blast near a cD galaxy, which is the largest class of galaxies in the universe that live at the center of galaxy clusters. Also at the center: a supermassive black hole with a gravitational force that pulls in cosmic debris and interstellar gas. But the black holes also can release an enormous amount of energy back into the universe, McNamara said. Jets of radio emission shoot out of the hole in beams, depositing particles, magnetic fields and energy.

Astronomers have been puzzled, however, about an apparent flaw in the galaxy life cycle: When interstellar gas eventually cools and matter accretes, the galaxy should form lots of new stars. But some galaxies produce few of these heavenly bodies. McNamara and his colleagues argue that gigantic space bubbles might be the culprits: The heat generated by the cavities prevents the gas from chilling down and creating stars.
The amount of energy contained in the shock wave created by the explosion also suggests that the supermassive black hole is gobbling up a greater amount of matter than scientists would have predicted. "It's like a 300 pound person eating 100 pounds of meat in one sitting," McNamara said.

Paul Nulsen, a scientist with the Harvard-Smithsonian Center for Astrophysics and the University of Wollongong who collaborated on the paper, also noted that the black hole must have grown tremendously to produce the huge explosion. "It tells us how (black holes) behave in a lot more detail than what we had before," he said.

The new study supports recent theories that supermassive black holes have a major impact on the structure of our universe, McNamara said. The volume of space the black hole occupies is about the same size of our solar system, he said, but it impacts a volume of space much greater than that - about 600 times the size of the Milky Way galaxy. "From this tiny region of space, the energy is spread out over enormous distances," he said.

The scientists next will conduct more detailed studies on the X-ray explosion and similar but smaller objects observed in other galaxy systems, Nulsen said. "By using more sophisticated modeling, we should get more information out of it," he said.

McNamara is a member of Ohio University's Astrophysical Institute and part of a new $1.4 million effort at the institution to examine mysteries surrounding the structure of the universe - from the tiniest quarks and protons to the largest phenomenon in space.

Other collaborators on the Nature paper are Michael Wise, MIT Center for Space Research; David Rafferty, Ohio University; Chris Carilli, National Radio Astronomy Observatory, Very Large Array; Craig Sarazin, University of Virginia; and Elizabeth Blanton, University of Virginia and Boston University.

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